It is well known that an extremely bright light which may contain a considerable amount of ultraviolet as well as infrared rays is produced by a welding operation. Extended exposure to such bright light rays may be very harmful to the welder's eye. Thus, it is a common practice that welders make use of a helmet with a protective light filter arranged in front of his eyes, or of a protective shield comprising a protective filter and manually held in place between the welder's eyes and a welding arc or flame.
A basic problem with such protective equipment is that the visible light is also greatly attenuated, making it difficult for the welder to clearly see the area of work at the beginning of the welding operation or after having finished it.